The US president is trying to stop transgender people signing up to the military.

Activist groups are turning to television ads — including on President Donald Trump's go-to station, Fox News — to pressure the White House into allowing transgender people to keep serving in the military.

Trump has vowed to ban transgender troops from serving. He'll be able to see the 30-second commercial as of Friday 2 March, when it starts airing on Fox, CNN, and MSNBC morning shows.

It uses a series of quotes from Trump, a former senior military leader and several Congress members who were in the armed forces to argue that all qualified Americans should be able to serve.

"An unfit president tweets that transgender Americans won't be allowed to serve," the ad says. "But decorated military leaders say there's no reason to single out these brave heroes."

Sarah McBride, Human Rights Campaign's spokeswoman, said it's a "critical window of time" to take the fight directly to the White House. The White House had no immediate comment.

The issue has become mired in a complicated string of political statements, court decisions and policy reviews since Trump first stunned his administration with tweets in July 2017 declaring that the government would ban transgender individuals from serving in the military.

He later asked Defense Secretary Jim Mattis to send him a recommendation on how to proceed. That memo has now been delivered to Trump. The White House has said that a quick decision is unlikely.

It's unclear how much impact the court decisions will have on Trump's decision. Activist groups worry the administration could enact such strict enlistment and health care restrictions that it would become all but impossible for transgender troops to join or continue serving.

"If they can't access health care, then they won't be able to serve," said McBride. "Then it becomes a ban in and of itself."

US President Donald Trump speaks during a meeting with state and local officials on school safety in the Roosevelt Room of the White House on February 22, 2018 in Washington, DCMANDEL NGAN/AFP/Getty Images

McBride didn't provide the exact cost of the ad buy, describing it as "five figures". She said it was the largest media campaign on this issue, with the backing of at least four other activist groups, including OutServe-SLDN, which represents the LGBT population in the military and is a plaintiff in the lawsuits.

In the last two months, several transgender people have visited recruiting stations for the military services and started the process of enlisting. The Pentagon says only one has made it through all the medical reviews, testing and paperwork and actually signed a contract. That person hasn't yet gone to basic training, but will likely do so in the coming months. The person hasn't been identified.

Under guidelines presented in December 2017, the Pentagon can disqualify potential recruits with gender dysphoria, a history of medical treatments associated with gender transition and those who underwent reconstruction.

Such recruits could be allowed in if a medical provider certifies they've been clinically stable in the preferred sex for 18 months and are free of significant distress or impairment in social, occupational or other important areas.

Transgender individuals receiving hormone therapy must be stable on their medication for 18 months.

The requirements make it challenging for a transgender recruit to pass. But they mirror conditions laid out by President Barack Obama's administration in 2016, when the Pentagon initially lifted its ban on transgender troops serving openly in the military.